Issues with 4k cable box on non 4k tv?

Is there any known issue with using an Xfinity 4k cable box on a non 4k TV?

I understand I'd only get the max resolution available on the TV (1080p for my TV) but is it safe to have that setup?

I had an older box that had latency issues while using streaming services. I switched it for a new box (was given a 4k box at the Xfinity store...model XG1v4 i think) that fixed the latency issues but the box would often reboot on its own (6x per day at least) got quite hot, and would stop working and require a reboot while watching streaming services through the box.

I swapped that one for the most current non 4k box (model XG2v2) but the latency returned.

Not sure if it's worth getting another 4k box in hopes that the one I had before was simply defective. 

Thoughts anyone?